A pressure sensor, as a sensor element, having a configuration in which, for example, resistors are bridge-connected measures a change in a resistance value of the resistors caused by distortion according to pressure by a voltage appearing between output terminals to thereby detect the pressure. In this case, an output of the sensor element fluctuates according to temperature of measurement environment. Consequently, in the case of using the sensor element in an environment in which temperature fluctuation is large or in the case where accurate detecting operation is necessary, correction of a detection signal according to temperature has to be performed.
In this case, conventionally, a sensor element performing detection by constant current driving for the purpose of eliminating the influence of temperature is used. It uses a technique of self-sensitivity compensation in which sensitivity temperature characteristic of an output of the sensor element is cancelled under constant current driving condition.
An application voltage Vg to a sensor element determining sensor element sensitivity is determined by a product of constant current Is passed to the sensor element and sensor element resistance Rg (Vg=Is×Rg). However, the application voltage Vg to the sensor element is regulated by saturation voltage Vsatp and threshold voltage Vtp of an output stage Pch transistor necessary for normal operation of a constant current circuit. A voltage decreased from power supply voltage Vcc only by Vsatp+Vtp is obtained at the maximum, and maximization of sensor element sensitivity is limited. The problem is influenced more as the voltage driving of a semiconductor element is becoming lower.